This invention relates to a hose clamp, particularly to a clamp for tightly connecting a plastic or rubber hose with the end of a metal tube.
The hose clamp is generally known which is manufactured by bending a piece of a metal sheet or wire into an annular shape to surround the hose. Preferably, the hose clamp always maintains the annular shape in a perfectly circular state and presses the entire annular surface of the hose uniformly with equal force, even if the hose clamp is applied to a hose having somewhat different outside diameters. The hose clamp, however, has been rarely available hitherto which can meet such demands as mentioned above. If the hose clamp meeting the demands is available, the hose clamp has serious defects in other respects. Hence the clamp cannot be satisfactory as a whole.
For example, in Japanese Patent Publication No. 51-3923 and Japanese Utility Model Publication No. 52-5308 is disclosed a hose clamp which is formed by bending an elastic band metal into an annular form to overlap both ends of the band metal, providing each of the ends with a finger grippable portion projecting in the outward direction and further, in order to equalize the elastic action of the sheet metal, providing the band metal symmetrically with one or more apertures in the form of a triangle or a narrow band. The hose clamp, however, has the disadvantages that the clamp is not economically manufactured because the apertures weaken the original elastic force of the band metal and the band metal should be employed having more thickness or width. Furthermore, the Japanese Utility Model Publication No. 53-19458 discloses a hose clamp in which sheet metal is bent in an annular form and provided with one or more projections extending symmetrically from the center in the circular direction with a progressively diminishing height in proportion to a distance from the center. The projection, however, must be formed by forcible extension of the sheet metal, which is liable to produce cracks in the metal and, accordingly, the hose clamp cannot be sufficient.
On the other hand, a C-shaped snap ring is known which is designed to always maintain its opening in a perfectly circular state. In the snap ring, the thickness thereof is increased to the maximum in the longitudinal center and progressively decreased up to the both ends thereof according to a distance from the center. Since the snap ring has no overlapping portions, such progressive decrease of the thickness up to the both ends is possible in the snap ring. However, the progressive decrease is impossible in the hose clamp because the hose clamp should have overlapping portions in the both ends to form finger grippable portions and must be opened by squeezing the finger grippable portions together. More particularly, in the hose clamp, the overlapping portions must be partly cut away to form mutually complementary parts extending in the annular direction, one of which is interposed between the other. Hence, there is produced a remarkable change in the width of the band metal. Thus, the progressive decrease in the thickness up to the ends is meaningless in the hose clamp because the remarkable change in the width produces an abrupt decrease in the pressing force.
Now it has been found that the hose clamp can always maintain the shape thereof substantially in a perfectly circular state if only the thickness is increased in the middle portion of the band metal. The present invention has been completed on this finding.